Is this really the best way to make a great roguelike?

Probably not. However, the short time frame forces the developer to actually plan on finishing. Normal roguelike design is open ended. One will still be working on the same roguelike years after starting. This can become dispiriting, as one may have new ideas that cannot fit inside one's current game. A 7DRL is a way to experiment with the genre without fearing creating another life-work. After seven days, one can wash one's hands of the roguelike.

Why seven days? Why not 24 hours?

Programming isn't an activity that I'd recommend be done in 24-hour marathons. Sure, it can be fun. But you don't learn much out of it, except maybe that programming with little sleep makes unreadable code.

Why seven days? Why not one month?

How do I do a 7DRL?

Choose a week to work on the roguelike. Post to [rec.games.roguelike.development] that you have started. After seven days passes, post to [rec.games.roguelike.announce] your successful creation.

Note that while a 7DRL could be written at any time, the denizens of [rec.games.roguelike.development] may on occasion organize a specific week for people to accept the challenge in. Such event is cleverly named the Seven Day Roguelike Challenge.

My roguelike took 10 days, but is really playable! Does it count?

It counts as a Ten Day Roguelike. (:

But is it a roguelike?

Usually the challenge produces many innovative twists on the traditional genre definitions, so don't be afraid to experiment. However, this is a roguelike-focused challenge, not just a generic game jam. Procedural content and permadeath/permafailure are both pretty core. Other high-value elements include control of a central character and an emphasis on player thought and decision-making rather than manual skill or execution.

Remember that in roguelikes game mechanics tend to be the primary focus, with graphics being a nice extra - be sure your gameplay is sharp before you worry about your visual polish. A pretty but shallow game would not normally be considered a good roguelike. Many 7DRLs use ASCII graphics so that the maximum time can be spent on making an interesting game.

Ultimately though only you decide if your game is as roguelike as you want it to be.

Can I use external libraries? Graphics files? Design documents? Code I wrote in the past? Existing roguelikes?

This is entirely up to the developer.

It is recommended one has some design idea going into the project.

You should say what pre-existing code you used. The goal isn't to see who can retype existing algorithms the fastest. The goal is for people to write playable and complete roguelikes.

Remember: if you spend seven days patching NetHack, you likely will end up with something that looks a lot like NetHack, so it would thus not be considered very impressive. However, if you spend seven days patching NetHack and create an amazing new roguelike, you will be suitably honored.

To be specific, writing a new T-Engine module or a libtcod-based game in seven days would be a 7DRL.

Not from scratch? Then what's the point?

Life shows that the biggest challenge in making a roguelike is actually finishing it. 7DRL is meant as a fun exercise in the very act of releasing a playable game. Using premade libraries does not make that part any easier, as proven by the yearly results.

How do we judge the winners?

The primary criterion is completeness. The resulting game should be complete and playable. The author is encouraged to not release another version.

That being said, the only true judge of your "winnerness" is yourself.

My friend and I want to work on a 7DRL together...

What about licensing?

Clearly, the compiled roguelike itself must actually be released. No good claiming you have it, but won't release it. (:

Source code does not have to be released, but it is strongly encouraged that you release it. Heck, release it public domain! It was only seven days work, after all. (Of course, if you patched existing code, follow its licensing agreement...)

So, I've done a 7DRL, but now I want to make it better!

You'll note under the "winners" section that the author is encouraged not to release another version. This isn't because we don't want to see bug fixes, or don't want to see the framework written for the 7DRL extended into an even better game. It is to try and push the participants to have something done and polished on day seven rather than "that will be added later..." It is quite sensible and good if people want to take their 7DRL (or, license depending, someone else's!) and extend/modify it into a full-fledged roguelike. For example, Martin Read's MPR7DRL formed the basis for Martin's Dungeon Bash and Slash's CastlevaniaRL:Prelude evolved into CastlevaniaRL.